This invention relates to programmable logic devices. More particularly, this invention relates to observing logic signals at the outputs of various programmable logic circuits on programmable logic devices and preloading data into such programmable logic circuits.
Programmable logic devices are integrated circuits that may be programmed by a user to perform various logic functions. As programmable logic devices become more complex, it is becoming desirable to observe the logic signals on internal device nodes in order to determine whether a device is functioning properly. The ability to observe such logic signals (e.g., at the outputs of logic elements or other programmable logic circuits) reduces test costs by reducing test development time and test run time during manufacturing. The ability to observe these logic signals also helps to reduce the time needed to successfully debug a given design for a programmable logic device. Being able to preload data into certain programmable logic circuits also reduces test costs and helps to reduce the time needed to debug a design.
It is therefore an object of the present invention to provide arrangements for observing logic signals from various programmable logic circuits on a programmable logic device.
It is another object of the present invention to provide arrangements for preloading data into certain programmable logic circuits on a programmable logic device.